Question: Simplify the following expression: $q = \dfrac{9}{5z} - \dfrac{1}{3z}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5z$ and $3z$ $\lcm(5z, 3z) = 15z$ $ q = \dfrac{3}{3} \cdot \dfrac{9}{5z} - \dfrac{5}{5} \cdot \dfrac{1}{3z} $ $q = \dfrac{27}{15z} - \dfrac{5}{15z}$ $q = \dfrac{27 -5}{15z}$ $q = \dfrac{22}{15z}$